1. Field of the Invention
The present invention relates to a semiconductive member having a coating film containing a conductive agent formed on the surface of a substrate such as an elastic material or a semiconductive member having a substrate composed of an elastic material and containing a conductive agent, such as a charge roller, development roller, transfer roller, toner feed roller or discharge roller mainly used as a member of an electrophotographic apparatus, and to an electrophotographic apparatus comprising the semiconductive member.
2. Description of the Prior Art
Members such as a charge roller, development roller, transfer roller, discharge roller and development blade have been used in an electrophotographic apparatus such as a printer, copier or facsimile. These members must have a resistance value within a semiconductive range.
In general, to control the resistance value of the above semiconductive member, various methods have been employed: one in which a resistance control layer, for example, a coating film is formed on an elastic material which is a substrate, a conductive material such as an ion, carbon or metal oxide is contained in the resistance control layer and the amount of the conductive material is controlled, and one in which a conductive material such as an ion, carbon or metal oxide is contained in an elastic material such as urethane or rubber which is a substrate and the amount of the conductive material is controlled.
However, when an ion is used, a variation in resistance is small but only a relatively high resistance range can be covered and the resistance is readily affected by the surrounding environment. In addition, the resistance is readily changed by energization and the ion readily bleeds to become a contamination source.
Meanwhile, when carbon or metal oxide is used, there are a lot of advantages that the resistance is hardly affected by the surrounding environment, the resistance is rarely changed by energization, a contamination problem rarely occurs, and a required resistance range can be covered. However, a variation in resistance is large and dependence of resistance on voltage is large. Then, in order to improve reproducibility and stability of resistance, attempts to add a dispersant together with the above conductive material are being studied. However, a new problem arises that the above additive itself readily becomes a contamination source.
It is an object of the present invention which has been made in view of the above problem to provide a semiconductive member having a small variation in resistance and stable resistance, which is advantageously used as a charge roller or development roller by modifying a conductive agent to be contained in a resistance control layer which is a coating layer or a conductive agent to be contained in an elastic material which is a substrate as well as an electrophotographic apparatus comprising this semiconductive member.